Add spec validators for the WRP messages (BAD BRANCH)

[denopink]

Overview

related to #25, #78, xmidt-org/scytale#88, xmidt-org/talaria#153 and builds on top of #80.

Note The diff looks big because we're waiting for #80 , we'll rebase when it's merged.

tl;dr

This pr introduces our wrp spec validators built with our validation framework introduced in #80 which only validates the opinionated portions of the spec. Clients can leverage these prebuilt validators to validate their messages.

Explanation

• Validates requirements described at https://xmidt.io/docs/wrp/basics/#overarching-guidelines
• Validates requirements described at https://xmidt.io/docs/wrp/basics/#locators
• Validates message type values
• Does not cover validators for a specific message type (future prs)

Clients can leverage our prebuilt validators to validate their messages. One set of these validators are our spec validators:

msgv, err := NewTypeValidator(
	// Validates found msg types
	map[MessageType]Validator{
		// Validates opinionated portions of the spec
		SimpleEventMessageType: SpecValidators,
		// Only validates Source and nothing else
		SimpleRequestResponseMessageType: SourceValidator,
	},
	// Validates unfound msg types
	AlwaysInvalid)
if err != nil {
	return
}

foundErrSuccess1 := msgv.Validate(Message{
	Type:        SimpleEventMessageType,
	Source:      "MAC:11:22:33:44:55:66",
	Destination: "MAC:11:22:33:44:55:61",
}) // Found success
foundErrSuccess2 := msgv.Validate(Message{
	Type:        SimpleRequestResponseMessageType,
	Source:      "MAC:11:22:33:44:55:66",
	Destination: "invalid:a-BB-44-55",
}) // Found success
foundErrFailure := msgv.Validate(Message{
	Type:        Invalid0MessageType,
	Source:      "invalid:a-BB-44-55",
	Destination: "invalid:a-BB-44-55",
}) // Found error
unfoundErrFailure := msgv.Validate(Message{Type: CreateMessageType}) // Unfound error
fmt.Println(foundErrSuccess1 == nil, foundErrSuccess2 == nil, foundErrFailure == nil, unfoundErrFailure == nil)
// Output: true true false false

Type of Change(s)

• Non-breaking Enhancement
• All new and existing tests passed.

[denopink]

I did something silly and this branch is kinda messed up. Easier to create new branch and pr and cherry-pick the desired commits.